This invention relates to a mid-sole or a sole of shoes, which seeks an effect of shock absorption during walking and also a massage effect owing to excitement of the sole of foot while providing for a comfortable sense of wear. Of course the invention is applicable to and covers sandals and the like.
In the prior art, it is well known that absorption of the shocks and massaging of the sole of foot during walking are effective for maintaining health. The applicant has earlier proposed a sole (or a mid-sole) of shoes, which comprises a bottom plate with a recess and a plurality of slanted blades formed therein and a flexible cover with the outer periphery thereof fused to the outer periphery of the top of the bottom plate, water being sealed in the recess (as disclosed in U.S. patent specification Ser. No. 189,816). When a person wearing shoes with such soles walks, the sealed water is moved in the recess to absorb shocks during the walking while providing a stable and comfortable sense of wearing. In addition, with adequate rigidity of the blades and action of water to alleviate the rigidity, the sole of foot can be excited continuously with an adequate strength not providing any pain even when the shoes are worn for long time.
However, the shoes using the above sole are subject to leakage of the sealed water. According to the examination, water leaks in a specific portion, i.e., a fore end portion touched by, for instance, little to middle fingers of the foot. The cause for this is investigated to find the following. Since the cover is formed with a recess having a shape corresponding to the sole of foot, the bottom plate portion corresponding to the recess is naturally reduced in thickness, and a portion corresponding to the little to middle foot fingers, particularly to the third finger, is always strongly pushed down and deformed when the shoe is about to be separated from the ground. With this force together with the urging force of water, the fused portion in the neighborhood of the portion contacted by the little to middle foot fingers is weakened to result in the leakage of water.